Historical retrospective · Bitcoin
BIP 68 introduced relative sequence-based time locks
BIP 68 gives transaction input sequence numbers a relative-locktime meaning, measured from the confirmation of the referenced output.
Relative timing conditions let a transaction express “wait this long after the earlier output” rather than rely only on an absolute calendar threshold.
That capability supports safer multi-step protocols and helped standardize tools used in later channel and contract designs.
Time-lock semantics are subtle; wallet and protocol authors must account for block-based versus time-based interpretation.
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